Lightly coat a 1-cup ramekin with nonstick cooking spray.
In a small bowl, whisk together the flour, baking powder, and salt. In a separate bowl, stir together the butter, Greek yogurt, and milk.* Stir in the vanilla and vanilla crème stevia. Gradually mix in the flour mixture, about 1 tablespoon at a time, until just incorporated. Gently fold in 6 blueberries.
Spread the batter into the prepared ramekin, and gently press the remaining blueberries on top. Microwave on 30% POWER for 2 minutes 40 seconds (2:40). Let the muffin cool for at least 2 minutes to allow the center to finish cooking through.